Timer services may be provided at an operating system level for various computer systems. Timer services may be used by various applications or other services to initiate various functions at a future time.
Timers may be defined in absolute and relative manners. In an absolute timer, the timer may be set to go off or respond at a specific time according to a system clock. A relative timer may be set to operate at a certain number of minutes or seconds after being set, without regard to the system clock.
Timer services may behave erratically or unpredictably when changes are made to a system clock. Changes may be made, for example, when the system changes time zones, during the change between daylight savings time and standard time occurs, or when the system clock is reset for some other reason, including slight adjustments to the clock to coordinate with another system.